1. Field of the Invention
The present invention relates to a device for exerting an external pressure on parts of a human body, more specifically, the present invention relates to a device designed to surround a body part so as, for example to make it easier for pilots to withstand the high acceleration forces to which they are subjected when making abrupt turns with high-performance aircraft or to improve the blood circulation in people having poor cardiac activity. In the first instance, the device is of the type which prevents blood from being drained from the brain, primarily to the arms, legs and the lower part of the torso, by exerting a pressure on these parts so as to prevent them from swelling and receiving additional blood. In the second instance, the device is of the type which "squeezes" the patient's legs at a certain rhythm to increase the blood flow therein.
2. Background of the Prior Art
Pilots who perform rapid changes of direction when flying at high speeds, are subjected to considerable acceleration forces, so-called G-forces. These cause blood to be driven away from the brain and out into the limbs and the lower part of the torso, which may cause disorders, such as pain, impaired judgment and, in serious cases, even unconsciousness. To counteract this effect, use is made of devices which prevent such body parts from swelling, such that they cannot receive additional blood. These devices originally consisted of laceable garments which surrounded the body parts and were so tightly strapped as to exert such a high external pressure on the body parts that these were unable to swell to any appreciable extent.
Since fighter aircraft have been developed to attain yet higher speeds and smaller turning radii, devices of this type have become out of date. The necessary pressures must then be so high that the devices cause considerable inconvenience if they are tight-fitting even when not required. Therefore, pilots have instead started using suits internally provided with double-walled casings, so-called bladders, which are filled with compressed gas so as to expand when pressure should be exerted on the body parts concerned.
In prior-art devices, the bladders are so designed as to cover the part of the body located below the waist and down to the ankles. To ensure proper function of the devices, one must have access to compressed air or any other gas in the aircraft, various valves and hoses for filling the bladders as well as a control system ensuring that the bladders produce an acceptable pressure on the body parts during flight.
One of the drawbacks inherent in the prior-art devices is that the flying suits become heavy and cumbersome. The use of bladders makes the suits very bulky. This depends, inter alia, on the fact that, in normal position, the bladders must often be maintained partly filled in order that the suit should react rapidly to changes of acceleration. They become rigid during flight, thus impeding the pilot's movement. Moreover, since the suits become very tight and warm, cooling is required.
These drawbacks will all be aggravated when aircraft development has come to the point that pilots should be able to withstand yet higher acceleration forces, which necessitates pressurizing additional parts of the body. The pressure-gas systems used and their mechanical components are already on the verge of reacting too slowly for the necessary rapid pressure increase to be achieved upon sudden changes of direction of the aircraft. In future aircraft generations, the drawbacks of these control systems will be increasingly pronounced.
To improve blood circulation, the known devices are of the same type as those used by pilots. Since the former also employ bladders, they too suffer from the same drawbacks, i.e. are complicated, heavy, rigid, and tight and react too slowly to be, for example, accurately controlled by the patient's cardiac rhythm.